Aggro works like normal, thats not the problem, well is part of the problem I guess, but no more so then having any other idiot show up and agro a couple of mobs and get the party annhilated. The problem is that assassins are melee combatants, and since the only other melee combatants are Warriors people assume that they can use their assassins as tanks and stand toe to toe with anyone, they just don't get that they have roughly 30 armor level less then warriors. The point of the assasins is to use a shadowstep skill to teleport to the enemy back line, let off a combo or two on one of the enemy casters and then port back to their team and recharge. They are burst combatants, outside of pulling off a combo, their damage stinks, their armor is low, and they are a drain on the enrgy of the monks that is needed to heal the competent members of the party.
Where are you using the Me/E? In PvE it can be pretty rough to find a group if you aren't a Monk or an Ele primary, Minion Master Necros do pretty well though, especially when you slap death nova and Dwayna's Sorrow on them. It turns the minions into bombs that explode on death, and the Dwayna's Sorrow is an AoE spell tha heals your entire party when anything affected by it dies so you can hit all your minions all at once, and then have 10 ambulatory heal parties.
